Hi all, this is my first posting. I am new to Meshmixer. I have a 3d model of the small aluminum part I am trying to make a 3d mold to hold the part tight on a fixture. I have plane cut the model where I want it. What I cant figure out is how to turn the plane cut of the model into a cavity in Meshmixer that I can 3d print. Can any one help?
BUILD A 3D PRINTED MOLD IN MESHMIXER FOR A FIXTURE
For a better view you can hide the printer's rendering via menu: View/ShowPrinter bed.
Now you need to construct a mold's stock. There are different ways to do that. Here's an easy way to construct a cubic stock:
Hit Ctrl+A (Cmd+A on Mac) to SelectAll of your model. In SELECT go to Edit/FitPrimitives and add a Plane (see tool settings in the image) as a separate object. Scale, translate or rotate it using the widget. Hit W to show the wireframe and set MeshDensity so the plane's resolution fits to the tessellation of your source object as good as possible.
Accept and SelectAll of the plane object. Go to Edit/Extrude and set Offset to include a half of the source:
Accept. Quit SELECT mode and activate the source object as a second object (hold down Shift while clicking it)
Now there're the boolean tools in EDIT. Run BooleanDifference:
I see...
You need to break the connection of inside and outside stuff and fill the holes:
Go to SELECT and set a small brush Size.
Paint a closed ring selection around each hole. Try to select nothing but planar regions:
Hit X to discard these faces. Now the outside shell isn't connected to the interior any more.
Select something at the interior shells and hit X to expand the selection to connected triangles:
Hit X to discard those faces and go to ANALYSIS/Inspector to close the open boundaries:
After hitting Accept you end up with a watertight surface.
Thanks again for all of the help. I am learning a lot. OK I need another bit of advise. There are locators on the actual part that was not included in the original model. I have 3D printed a prototype fixture and had to dremel out relief in the fixture to accommodate the locators. each locator is approx. 35mm long, 14mm wide, & 3.5mm deep. What is the simplest way to add these reliefs to my meshmixer model?
Two hints concerning your boolean result above:
- if you disable AutoReduceResult you'll get nicer intersections in the accepted result (at costs in file size)
- there still seem to be isolated particles (those blue lines). You should get rid of them selecting some area on the stock > hitting E to ExpandToConnected > hitting I to Invert and finally X to discard.
Now, I think you'll need some accuracy to add the locators, so this is the workflow I would do on your positive scan. I assume that the parting line of the casting holds is visible on the scan.
First of all: Scans might not be aligned to the world axes properly. So the first steps are to make sure that the measurements we'll use later on will hit the part as intended.
Here's some arbitrary position:
To align it to world axes append a plane object (from menu:File/ImportPlane) and set it to be a target via magnet icon in the object browser.
Now using EDIT/Transform move and rotate the source part so its base roughly fits to the plane:
Navigate to bottom view and select the area which should fit to the ground.
Run Edit/AlignToTarget
This finds a best matching orientation(rotation). But to be sure we move the source object to the ground plane again using EDIT/Align:
Now release the plane from being a target and rotate it 90°(without moving it) so it stands vertically and still hits the origin.
Now switch to the source object and in top view rotate around Y and move it so its casting seam fits to the plane:
Now we have it in a known coordinate system.
To be continued...
Now before deleting the plane we want to save its position dropping a pivot on it:
A pivot can be activated and transformed as any object. To show pivots in the object browser click the pivot icon in the lower left of the browser next to the cube icon. Delete the plane , activate the pivot and run EDIT/Transform.
Make sure that the widget shows the A,S and W circles in green. In this Absolute Snapping in World coordinates mode the values TranslateX, TranslateY, TranslateZ show its current position. Let's set all those values to zero (clicking on the numbers in the tool fly-out) and hit D to drop a duplicate there. Now input the lower Y distance of the lower locator in TranslateY, hit Enter and D to drop a duplicate on this position:
Continue to put in the needed Y values each time creating a duplicate. When done in Y put in the width of the locators in X. You should end up like:
We want to use EDIT/PlaneCut to construct the shape of the locators "top" on the scan. Run it. While PlaneCut is the active tool the cutting plane snaps to a pivot clicking on it (clicking it several times iterates in XZ, YZ, YX). Seems you need some rotation. While dragging on a rotation bow move the mouse away from the widget's center until a degree wheel appeared. Over it the plane snaps to degree increments. When you have the right orientation set the tool's CutType = SliceGroups and Accept.
Repeat the "horizontal" cuts until:
Now do the needed two vertical cuts running PlaneCut the same way but clicking the pivots (one of the inline pivots and the X-offset pivot) three times:
Now be have two groups we want to use. In Select select them by double click and run Edit/Extrude. Set the needed Offset, the Direction=ZAxis and the EndType=Flat.
Now we added the locators but the transition is too sharp.
There's a nice trick to bevel inside edges using EDIT/MakeSolid. Its SolidType=Accurate allows to set an offset. Set a positive offset (= bevel radius) and a sufficient SolidAccuracy and MeshDensity:
Now we have a hull from where we do MakeSolid again with the same, but now negative offset:
The part beveled that way(red) fits to the sharp one again:
Wow, you are good! It will take me some time to digest your instructions and try it out. thanks again. When I get caught up to remaking my cavity, my next question will be how to add the bolt holes in my model instead of drilling through the plastic. my prototype is seen below. another thing I noticed is the fit is not quite right. I think I forgot to scale my 3d print up. Do you think 1% is enough?
Virtual drilling is easy:
Let's assume a cubic object. Its length and width is 200mm (for easier calculation). Use EDIT/Align with Source=BasePoint and Destination=WorldOrigin/Y-Up to align its base to the origin. Now its base corner coordinates are at A = (X=100, Z=100), B =(X=100, Z=-100), C = (X=-100, Z=-100), D = (X=-100, Z=100), right?
Now we want to drill 4 holes with their centers in a distance of 20 to the edge.
Drop a pivot somewhere at the base plane ( or the upper plane) and run EDIT/Transform on it:
In the tool flyout set TranslateX = 80 and TranslateZ = 80. Hit D to drop a pivot there
Now set these parameter to -80,80 and hit D > set them to -80,-80 and hit D > set them to 80, -80 and Accept finally:
Now MESHMIX solid parts snap to pivots if you drag them near to a pivot. So drop a MESHMIX/Primitives cylinder onto the object, set the desired hole diameter at Dimension and drag it near a pivot until it snaps to it. Hit D to drop a duplicate there
(Note: Duplicates are not visible in DropSolid until you click Accept finally but they appear in the object browser). Drag it to the next pivot and hit D, drag it to the next pivot and hit D , drag it to the last pivot and hit Accept.
Activate all those cylinders and run EDIT/Combine.
Run EDIT/Transform and scale/move them in Y (green) until they reach through the cubic object.
Now activate the cubic as the first object and the cylinders as the second one and run BooleanDifference. (Don't forget to disable AutoReduceResult at low poly objects):
OK I am stuck. I don't know how to move the source object to the ground plane using EDIT/ALIGN
I want to thank you for all your help on this project. I got lost on that last bit trying to add material to the model for locator reliefs in the cavities. I could not keep spending so much time trying to figure out how to do it in MM. with the help of a colleague I was able to complete the project in IronCad quickly and easily.
I'm not giving up on MM as I also have it in my home for my own 3D printing work. I'll keep working at it.
Thanks again!
